PUCCH resource compression for EPDCCH in TDD mode

ABSTRACT

Techniques are described for compressing the PUCCH resources reserved for acknowledging downlink data transmissions when those resources are implicitly signaled by EPDCCHs that schedule the downlink transmissions in TDD mode. An acknowledgement resource offset field transmitted in the EPDCCH is configured to correspond to one or more values that compress the region in PUCCH resource index space that would otherwise be reserved for the subframes of a bundling window.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.15/386,404, filed Dec. 21, 2016, now issued as U.S. Pat. No. 9,872,282,which is a continuation of U.S. patent application Ser. No. 14/652,590,filed Jun. 16, 2015, now issued as U.S. Pat. No. 9,532,316, which is aU.S. National Stage Application under 35 U.S.C. 371 from InternationalApplication No. PCT/US2013/075830, filed Dec. 17, 2013, which claims thebenefit of priority to U.S. Provisional Patent Application Ser. No.61/752,186, filed Jan. 14, 2013, each of which are incorporated hereinby reference in their entirety.

TECHNICAL FIELD

Embodiments described herein relate generally to wireless networks andcommunications systems.

BACKGROUND

In LTE (Long Term Evolution) cellular systems, as set forth in the LTEspecifications of the 3rd Generation Partnership Project (3GPP),terminals (where a terminal is referred to in LTE systems as userequipment or UE) connect to a base station (referred in LTE systems asan evolved Node B or eNB) that provides connectivity for the UE to othernetwork entities of the LTE system that connect to an external networksuch as the internet. A major feature of LTE-Advanced (Long TermEvolution-Advanced or LTE-A), as part of the LTE specifications by the3rd Generation Partnership Project (3GPP), is increased support formulti-user MIMO (multi-input multi-output) in which spatial multiplexingis used to provide separate downlink and uplink communications pathsbetween an eNB and multiple UEs. As more UEs are scheduled per subframefor multi-user MIMO operations, the demand for physical downlink controlchannel (PDCCH) resources to provide scheduling for physical uplinkresources is increased. The design of the PDCCH in Releases 8/9/10 ofthe LTE specification provides for a maximum PDCCH size of three OFDM(orthogonal frequency division multiplexing) symbols in a subframe whichis inadequate for meeting this increased demand. Consequently, anothercontrol channel design, referred to as an enhanced PDCCH (EPDCCH), wasintroduced in Release 11 of the LTE specification.

In LTE, terminals that receive downlink data from the eNB may transmitacknowledgements (either positive or negative) back to the eNB over thephysical uplink control channel (PUCCH) using an uplink resourceallocated for that purpose by the eNB. In order to save signalingoverhead, the current LTE specifications allow the eNB to signal theterminal what uplink resource to use for the PUCCH as a function of thestructure of the information contained in the PDCCH or EPDCCH used togrant the terminal the downlink resource over which the terminalreceives the downlink data that is to be acknowledged. Efficientlyallocating uplink resources for the PUCCH via implicit signaling basedupon the structure of the information contained in the EPDCCH is aconcern of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a UE and an eNB in accordance with some embodiments.

FIG. 2 illustrates a bundling window and the PUCCH resource indices forthe subframes.

FIG. 3 illustrates a bundling where PUCCH resource calculation with alarge negative value for the ARO is used to shift the PUCCH resourceindex range for subframes S₂ to S₄ to the range of subframe S₁.

FIG. 4 is a table that illustrates the mapping of a two-bit ARO field toARO values.

DETAILED DESCRIPTION

LTE uses a combination of forward error-correction coding and ARQ(automatic repeat request), referred to as hybrid ARQ. Hybrid ARQ usesforward error correction codes to correct some errors. When uncorrectederrors are detected, the corrupted transmissions are discarded and thereceiver requests retransmission. As the term is used herein, ahybrid-ARQ acknowledgement may either be a negative acknowledgement(NACK), signifying that a transmission error has occurred and that aretransmission is requested, or a positive acknowledgement (ACK)indicating that the transmission was received correctly.

When the eNB transmits data to a UE, the UE requires allocation ofuplink resources by the eNB in order to respond with a hybrid-ARQacknowledgement. Described herein is an EPDCCH configuration andtechniques by which such uplink resources may be dynamically allocatedto the UE in cases where the allocation of the downlink resources isover an EPDCCH.

LTE Air Interface

FIG. 1 shows an example of a UE 100 and an eNB 150. The UE and eNBincorporate processing circuitries 110 and 160, respectively. Theprocessing circuitry 110 in the UE is interfaced to a plurality of REtransceivers 120 that are each connected to one of a plurality ofantennas 130. The processing circuitry 160 in the eNB is interfaced to aplurality of RF transceivers 170 that are each connected to one of aplurality of antennas 180. The illustrated components are intended torepresent any type of hardware/software configuration for providing anLTE air interface and performing the processing functions as describedherein.

The LTE air interface, also referred to as the radio access network(RAN), has a protocol architecture that may be basically described asfollows. The topmost layer in the user plane is the packet datacompression protocol (PDCP) layer which transmits and receives IP(internet protocol) packets. The topmost layer of the control plane inthe access stratum between the UE and eNB is the radio resource control(RRC) layer. The PDCP layer communicates with the radio link control(RLC) layer via radio bearers to which IP packets are mapped. At themedium access control (MAC) layer, the connection to the RLC layer aboveis through logical channels, and the connection to the physical layerbelow is through transport channels. The MAC layer handlesmultiplexing/demultiplexing between the logical channels, hybrid-ARQoperations, and scheduling, the latter being performed solely at theeNodeB for both the uplink and the downlink. Data in a transport channelis organized into transport blocks, with respect to which the hybrid-ARQfunction is performed at both the UE and eNB. The primary transportchannels used for the transmission of data, the uplink shared channel(UL-SCH) and downlink shared channel (DL-SCH), are mapped to thephysical uplink shared channel (PUSCH) and physical downlink sharedchannel (PDSCH), respectively, at the physical layer.

The physical layer of LTE is based upon orthogonal frequency divisionmultiplexing (OFDM) for the downlink and a related technique,single-carrier frequency division multiplexing (SC-FDM), for the uplink.In OFDM/SC-FDM, complex modulation symbols according to a modulationscheme such as QAM (quadrature amplitude modulation) are eachindividually mapped to a particular OFDM/SC-FDM subcarrier transmittedduring an OFDM/SC-FDM symbol, referred to as a resource element (RE). AnRE is the smallest physical resource in LTE. LTE also provides for MIMO(multi-input multi-output) operation where multiple layers of data aretransmitted and received by multiple antennas and where each of thecomplex modulation symbols is mapped into one of the multipletransmission layers and then mapped to a particular antenna post. EachRE is then uniquely identified by the antenna, port, sub-carrierposition, and OFDM symbol index within a radio frame as explained below.

LTE transmissions in the time domain are organized into radio frames,each having a duration of 10 ms. Each radio frame consists of 10sub-frames, and each sub-frame consists of two consecutive 0.5 ms slots.Each slot comprises six indexed OFDM symbols for an extended cyclicprefix and seven indexed OFDM symbols for a normal cyclic prefix. Agroup of resource elements corresponding to twelve consecutivesubcarriers within a single slot is referred to as a resource block (RB)or, with reference to the physical layer, a physical resource block(PRB).

In the case of FDD (frequency division duplex) operation, where separatecarrier frequencies are provided for uplink and downlink transmission,the above-described frame structure is applicable to both the uplink anddownlink without modification. In TDD (time division duplex) operation,subframes are allocated for either uplink or downlink transmission witha special subframe occurring at the transition from downlink to uplinktransmission (but not at the transition from uplink to downlinktransmission). The eNB manages the allocation of uplink and downlinksubframes within each radio frame during TDD operation.

LTE Control Signaling

A physical channel corresponds to the set of time-frequency resourcesused for transmission of a particular transport channel, and eachtransport channel is snapped to a corresponding physical channel. Thereare also physical control channels without a corresponding transportchannel that are needed for supporting the transmission of the downlinkand uplink transport channels. These include the physical downlinkcontrol channel (PDCCH) and the enhanced physical downlink controlchannel (EPDCCH), by which the eNB transmits downlink controlinformation (DCI) to the UE, and the physical uplink control channel(PUCCH) that carries uplink control information (UCI) from the UE to theeNB. Insofar as is relevant to the present disclosure, the DCI carriedby the PDCCH or EPDCCH may include scheduling information that allocatesuplink and downlink resources to the UE, while the UCI carried by thePUCCH may include hybrid-ARQ acknowledgements for responding totransport blocks received by the UE.

Each downlink LTE subframe is divided into a control region at thebeginning part of the subframe (i.e., the first two, three, or four OFDMsymbols) and a data region which makes up the remainder of the subframe.The control region is reserved for downlink control channels such as thePDCCH, and PDCCHs are transmitted only in the control region of asubframe. EPDCCHs, on the other hand, are transmitted in the data regionof a downlink subframe. In order to receive an EPDCCH, a terminal isconfigured with one or two sets of physical resource blocks over whichEPDCCH transmission to that terminal may occur. Each set consists oftwo, four, or eight PRB pairs, and the two sets may be of differentsize. The resource-block pairs may be flexibly and non-contiguouslylocated across the full downlink system bandwidth. A PRB pair belongingto an EPDCCH set but not used for EPDCCH transmission to a particularterminal in a certain subframe can be used for data transmission, eitherto the same terminal or to another terminal. Art EPDCCH set may beconfigured as either a localized or distributed set. In a localized set,a single EPDCCH is mapped to one physical resource-block pair and toadditional PRB pairs only as needed. In a distributed set, a singleEPDCCH is distributed over multiple PRB pairs. Also, in the ease ofmulti-antenna transmission by the eNB, an EPDCCH is transmitted usingDMRS (demodulation reference signal) based antenna pre-coding. A PDCCH,in contrast, is transmitted by the eNB using CRS (cell-specificreference signal) based transmit diversity.

The mapping of PDCCHs to resource elements is done with a particularstructure based on control channel elements (CCEs), where a CCE is a setof thirty-six contiguous resource elements. The number of CCEs requiredfor a certain PDCCH depends on the size of the DCI being carried. CCEsare numbered (i.e., indexed) according to their time-frequency locationin the control region subframe so that each PDCCH in a subframe isuniquely identified by the indexes of the CCEs that make it up. EPDCCHsare constructed from what are called enhanced control channel elements(ECCEs) as opposed to the CCEs used for construction a PDCCH. ECCEs arealso indexed according to their time-frequency location in the subframe.Unlike the indexing of CCEs, however, the indexing of ECCEs isterminal-specific.

Each PDCCH or EPDCCH may be addressed to a specific UE by appending aUE-specific CRC (cyclic redundancy check) to the PDCCH or EPDCCH, whichalso serves for error detection. Thus, a UE detects a PDCCH intended forit by performing the CRC calculation and seeing whether the calculationchecks. The CRC is made UE-specific by including the UE's (or UEs')radio network temporary identifier (RNTI) in the CRC calculation. LTEalso defines search spaces to limit the set of CCEs or ECCEs that the UEneeds to monitor in order to detect a PDCCH or EPDCCH intended for it.

If a UE has already been allocated PUSCH resources in an uplink subframein which control signaling such as a hybrid-ARQ acknowledgement is to besent, the control signaling can be time multiplexed with data in thePUSCH. Otherwise, the PUCCH is used. Each PUCCH resource is made up ofone resource block within each of two slots of an uplink subframe.Control signaling from multiple UEs can be multiplexed into a singlePUCCH region with a combination of time-domain and frequency-domain codedivision multiplexing. A symbol constituting the control signaling ismultiplied by an orthogonal cover sequence to effect spreading in time,and the resulting symbols are then used to modulate a phase rotated(corresponding to a cyclic shift in the time domain) length-12 referencesignal sequence in the frequency domain to effect spreading infrequency. The resource used by a PUCCH is thus not only specified inthe time-frequency domain by its assigned resource blocks, but also bythe cyclic shift and orthogonal cover sequence applied. By assigningdifferent cyclic shifts and orthogonal cover sequences to different UEs,PUCCHs may be transmitted by different UEs using the same time-frequencyresource.

A hybrid-ARQ acknowledgement is sent via a single BPSK or QPSK (binaryor quadrature phase shift keying) symbol that is code divisionmultiplexed in a PUCCH in the manner just described to spread the symbolover the pair of resource blocks in what is referred to as a Format 1PUCCH. A PUCCH format 1 resource is represented by a PUCCH index,n_(PUCCH) ⁽¹⁾, from which the resource block pair, the phase rotation,and the orthogonal cover sequence are derived in the manner described bythe LTE specifications (See 3GPP TS 36.211).

To provide transmit diversity for the PUCCH, the PUCCH may also betransmitted using two antenna ports using a technique called SpatialOrthogonal Resource Transmit Diversity (SORTD). In SORTD, the same PUCCHis transmitted using two different PUCCH indices.

Downlink scheduling assignments to a UE apply to the same subframe inwhich they are transmitted. In the situation where a UE receives a PDSCHallocation in a particular subframe, the UE needs to send a hybrid-ARQacknowledgement in a designated subsequent subframe. The UE may use apreviously allocated uplink resource in that subsequent subframe (i.e.,either a PUSCH or PUCCH resource). Otherwise, for a hybrid-ARQacknowledgement in a format 1 PUCCH, the eNB allocates the uplinkresource in the same PDCCH that allocates the PDSCH containing the datawhich is to be acknowledged.

In the case of FDD, there is a one-to-one correspondence betweendownlink subframes transmitting data and uplink subframes transmittinghybrid-ARQ acknowledgements for that data. In TDD, on the other hand, anasymmetric allocation of uplink and downlink subframes may necessitatethat a single uplink subframe be used to acknowledge multiple downlinksubframes, the latter group of downlink subframes being referred to as abundling window. Although, in principle, multiple PUCCHs could be usedby a terminal to acknowledge multiple downlink subframes, current LTEspecifications dictate that there is only one PUCCH per terminal persubframe. If a terminal needs to send more acknowledgements than thereare bits allocated for in a PUCCH (two bits for a Format 1 PUCCH), atechnique called resource selection (a.k.a., channel selection) isemployed. In this technique, the eNB assigns multiple PUCCH resources tothe terminal, for acknowledging multiple downlink transmissions in asubsequent uplink subframe. Although all of these PUCCH resources arereserved and cannot be used for other purposes, the terminal selectsonly one of the reserved PUCCH resources to actually transmit the PUCCH.Which of the reserved PUCCH resources is selected by the terminalconstitutes additional information for the eNB that may be interpretedas a particular pattern of positive and negative acknowledgements forthe multiple downlink subframes.

PUCCH Mapping Schemes for EPDCCH

To reduce signaling overhead, the eNB implicitly signals the resourcefor a format 1a/b PUCCH that is to be used to acknowledge one or morePDSCH transmissions by including that information in the structure ofthe PDCCH or EPDCCH that allocates the PDSCH to the terminal.Specifically, the PUCCH resource is a function of the lowest index ofthe CCE or ECCE used to construct the PDCCH that schedules the PDSCHtransmission.

For PDCCH-scheduled downlink transmissions, the resource index to usefor a hybrid-ARQ acknowledgement is given as a function of the first CCEin the PDCCH used to schedule the downlink transmission to the terminal.There is then no need to explicitly include information about the PUCCHresources in the downlink scheduling assignment. Since hybrid-ARQacknowledgements are transmitted a fixed time after the reception of thePDSCH, the eNB knows when to expect a hybrid-ARQ on the assigned PUCCHresource.

For EPDCCH-scheduled transmissions, however, the index of the first ECCEin the EPDCCH cannot be used alone. Since the ECCE indexing isconfigured per terminal and is terminal-specific, two differentterminals with EDPCCHs on different PRBs may have the same number of thefirst ECCE in the EPDCCH. The current LTE specifications thereforeprovide an acknowledgement resource offset (ARO) field in the EPDCCHthat enables the eNB to adjust the index of the PUCCH resourcecalculated by the terminal based upon the lowest ECCE index of theEPDCCH. The eNB uses the ARO to avoid collisions between multiple PUCCHresources assigned to a terminal or between the PUCCH resources assignedto different terminals. The eNB also configures an additional parameter,N_(PUCCH,q) ^((e1)), via RRC signaling that is used in the calculationof the PUCCH resource index by the terminal. The N_(PUCCH,q) ^((e1))parameter is an offset configured by the eNB to separate PUCCH resourceindices computed for a particular EPDCCH set q from those computed forother EPDCCH sets. Different EPDCCH sets assigned to different terminals(or assigned to the same terminal) may thus be assigned PUCCH resourcesseparated in the PUCCH resource index space by the value of N_(PUCCH,q)^((e1)).

For FDD mode, a format 1a/b PUCCH resource for an EPDCCH may becalculated as:n _(PUCCH) ⁽¹⁾ =n _(ECCE,q)+Δ_(ARO) +N _(PUCCH,q) ^((e1))for an EPDCCH set q configured for distributed transmission to the UEand as

$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCH,N_(PUCCH,q) ^((e1)) is an offset configured by the eNB to separate PUCCHresource indices computed for EPDCCH set q from those computed for otherEPDCCH sets, Δ_(ARO) is the value of the ARO contained in the DCI of theEPDCCH, N_(RB) ^(ECCE,q) is the number of ECCEs in a resource block, andn′ is a number between 0 and 3 determined from the DMRS (demodulationreference signal) antenna port used for localized EPDCCH transmission.If the PUCCH is to be transmitted using SORTD, the calculated resourceindex is used for one antenna port and incremented by one for the otherantenna port. By appropriate setting of the ARO and N_(PUCCH,q) ^((e1)),the eNB attempts to avoid PUCCH resource indices assigned to differentEPDCCHs. For FDD, the ARO may be selected by the eNB from the followingset: {−2, −1, 0, 2}. By including both 1 and 2 (or −2) in the set, theeNB is able to separate PUCCH resource indices in the eases where SORTDis employed or not employed to transmit the PUCCH.

For TDD mode, the situation is complicated by the fact that EPDCCHsbelonging to a particular set configured for a terminal may occur inmultiple subframes belonging to a bundling window that must beacknowledged by a single PUCCH transmission. To separate the PUCCHresources for the different subframes of bundling window in PUCCHresource index space, the calculations given above for FDD mode may bemodified to include a term that includes the sum of the number of ECCEsin the EPDCCH set configured for the terminal in each subframe of thebundling window. The PUCCH resource may then be computed as:

$n_{PUCCH}^{(1)} = {n_{{ECCE},q} + {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for distributed transmission to the UEand as

$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCHtransmitted in subframe m, N_(PUCCH,q) ^((e1)) is an offset configuredby the eNB to separate PUCCH resource indices computed for EPDCCH set qfrom those computed for other EPDCCH sets, Δ_(ARO) is the value of theARO contained in the DCI of the EPDCCH, N_(ECCE,q,i) is the number ofECCEs configured for EPDCCH set q in a subframe with relative index i,N_(RB) ^(ECCE,q) is the number of ECCEs in a resource block, and n′ is anumber between 0 and 3 determined from the DMRS (demodulation referencesignal) antenna port used for EPDCCH transmission in subframe m. Again,if the PUCCH is to be transmitted using SORTD, the calculated resourceindex is used for one antenna port and incremented by one for the otherantenna port.

The same set of permissible ARO values used for FDD mode, where the AROvalue is selected from {−2, −1, 0, 2}, could also be used for TDD mode.A problem with the way of allocating PUCCH resources in TDD mode as setforth above, however, is that PUCCH resources are effectively reservedfor subframes of the bundling window whether or not ECCEs are actuallyutilized in EPDCCHs for those subframes. FIG. 2 illustrates a bundlingwindow consisting of subframes S₁ through S₄. The subscripts refer totheir relative indices within the bundling window so that S₁ is theearliest subframe and S₄ is the latest subframe. For each subframe S₁,N_(ECCE,i) is the number of ECCEs configured for EPDCCH in thatsubframe. The PUCCH resource index calculation for TDD mode as givenabove with no ARO compensation would mean that the PUCCH resource indexcalculated for subframe S₄ would be calculated in a manner that reservesPUCCH resources for subframes S₁ through S₃ regardless of whether EPDCCHtransmissions actually occur in those subframes. That is, the sum ofN_(ECCE,1) through N_(ECCE,4) is reserved in the PUCCH resource indexspace. It is desirable to minimize the amount of resources reserved forPUCCH transmission because those resources can be allocated instead toPUSCH transmissions to increase throughput.

A way to improve the situation is to provide permissible values for theARO that effectively compress the PUCCH resources. That is, the eNB isable to signal the terminal with an appropriate ARO that compresses theregion in PUCCH resource index space that would otherwise be reservedfor the subframes of a bundling window. Accordingly, in one embodiment,the value of the ARO may be selected from the following set of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} - 1},0,2} \right\}.$The large negative values represented by the first two elements of theset value can be used to shift the PUCCH resource index for a subframein the bundling window to a range used for acknowledging PDSCHtransmissions in the earliest subframe of the bundling window. For theearliest subframe of the bundling window, the large negative values arenot needed, and the ARO could be selected from the same set used for FDDmode: {−2, −1, 0, 2} where the nested property can hold. FIG. 3illustrates the bundling window consisting of subframes S₁ through S₄where PUCCH resource calculation with a large negative values the AROcan be used to shift the PUCCH resource index range for subframes S₂ toS₄ to the range of subframe S₁.

FIG. 4 is a table that illustrates an embodiment as just described. Fora downlink subframe having a relative index m between 1 and M−1 with Mbeing the number of subframes in the bundling window and with m=0representing the earliest subframe, the value of the two-bit ARO fieldin the DCI of an EPDCCH is interpreted to correspond to one of thevalues in the set of elements made up of

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} - 1},0,2} \right\}$as indicated by the table in FIG. 4. In one embodiment, if m=0, thevalue of the two-bit ARO field corresponds to one of the following setof elements: {−2, −1, 0, 2}.

In another embodiment, for a downlink subframe having a relative indexm>0, the value of the ARO is selected from a set that includes thefollowing set of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} - \alpha},{{- {\sum\limits_{i = 0}^{m - 1}n_{{ECCE},q,i}}} + \beta}} \right\}$where α and β are specified integers. In another embodiment, for adownlink subframe having a relative index m>0, the value of the ARO isselected from the following set of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \alpha},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \beta},0,2} \right\}$where α and β are specified integers. In either of the aboveembodiments, the integer values may be selected as α=0 and β=2.

ADDITIONAL NOTES AND EXAMPLES

In Example 1, a method for operating an evolved Node B (eNB) an LTE(Long Term Evolution) network, comprises: via an enhanced physicaldownlink control channel (EPDCCH) made up of indexed enhanced controlchannel elements (ECCEs), transmitting downlink control information(DCI) to a UE that grants a physical downlink shared channel (PDSCH)resource for a downlink subframe belonging to a bundling window andassigning a physical uplink control channel (PUCCH) resource index tothe UE for acknowledging the PDSCH transmission calculated as a functionof the lowest index of the ECCEs used to construct the EPDCCH added tothe number of ECCEs in EPDCCHs configured for the UE in earliersubframes that belong to the bundling window and added to one of twospecified integer values; and, transmitting an acknowledgment resourceoffset (ARO) in an ARO field of the DCI that instructs the UE to shiftthe PUCCH resource index by an amount equal to the value of the ARO andwherein, except for the earliest subframe of the bundling window, valuesfor the ARO are selected from a group that includes a value that shiftsthe PUCCH resource index to a range used for acknowledging PDSCHtransmissions in the earliest subframe of the bundling window.

Example 2, a method for operating a UE in TDD mode comprises: receivingdownlink control information (DCI) from an eNB via an enhanced physicaldownlink control channel (EPDCCH) made up of indexed enhanced controlchannel elements (ECCEs) that grants a physical downlink shared channel(PDSCH) resource for a downlink subframe belonging to a bundling window,calculating a physical uplink control channel (PUCCH) resource index foracknowledging the PDSCH transmission as a function of the lowest indexof the ECCEs used to construct the EPDCCH added to the number of ECCEsin EPDCCHs configured for the UE in earlier subframes that belong to thebundling window; and, interpreting the of value an acknowledgmentresource offset (ARO) field of the DCI as corresponding to an ARO valuethat shifts the PUCCH resource index by an amount equal to the value ofthe ARO and wherein, except for the earliest subframe of the bundlingwindow, values for the ARO corresponding to the ARO field are selectedfrom a group that includes a value that shifts the PUCCH resource indexto a range used for acknowledging PDSCH transmissions in the earliestsubframe of the bundling window.

In Example 3, an eNB comprises processing circuitry and a radiointerface for communicating with user equipments (UEs), wherein theprocessing circuitry when operating in time division duplex (TDD) modeis to perform the method of Example 1.

In Example 4, a UE comprises processing circuitry and a radio interfacefor communicating with an eNB, wherein the processing circuitry whenoperating in time division duplex (TDD) mode is to perform the method ofExample 2.

In Example 5, the subject matter of any of Examples 1 through 4 mayoptionally include: wherein, for a downlink subframe having a relativeindex m between 0 and M−1 with M being the number of subframes in thebundling window and with m=0 representing the earliest subframe, thePUCCH resource index n_(PUCCH) ⁽¹⁾ used to determine the resource blockpair, cyclic shift, and orthogonal cover sequence of a format 1 PUCCHand is computed as:

$n_{PUCCH}^{(1)} = {n_{{ECCE},q} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for distributed transmission to the UEand

$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCHtransmitted in subframe m, N_(PUCCH,q) ^((e1)) is an offset configuredby the eNB to separate PUCCH resource indices computed for EPDCCH set qfrom those computed for other EPDCCH sets, Δ_(ARO) is the value of theARO contained in the DCI, N_(ECCE,q,i) is the number of ECCEs in EPDCCHset q configured for the UE in a subframe with relative index i, N_(RB)^(ECCE,q) is the number of ECCEs in a resource block, and n′ is a numberbetween 0 and 3 determined from the DMRS (demodulation reference signal)antenna port used for EPDCCH transmission in subframe m.

In Example 6, the subject matter of Example 5 may optionally include:wherein if the PUCCH is to be transmitted over two antenna ports usingspatial orthogonal-resource transmit diversity (SORTD), the PUCCHresource index n_(PUCCH) ⁽¹⁾ is computed for one antenna port andincremented by 1 for the other antenna port.

In Example 7, the subject matter of Example 5 may optionally include:wherein, for m>0, the value of the ARO is selected from the followingset of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 1},0,2} \right\}.$

In Example 8, the subject matter of Example 5 may optionally include:wherein, for m=0, the value of the ARO is selected from the followingset of elements: {−2, −1, 0, 2}.

In Example 9, the subject matter of Example 5 may optionally include:wherein, for m>0, the value of the ARO is selected from a set thatincludes the following set of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \alpha},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \beta}} \right\}$where α and β are specified integers.

In Example 10, the subject matter of Example 5 may optionally include:wherein, for m>0, the value of the ARO is selected from the followingset of elements:

$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \alpha},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} + \beta},0,2} \right\}$where α and β are specified integers.

In Example 11, the subject matter of Example 9 or 10 may optionallyinclude: wherein α=0 and β=2.

In Example 12, the subject matters of any of Examples 1 through 11 mayoptionally include: wherein the ARO field is a two-bit field.

In Example 13, the subject matters of any of Examples 1 through 12 mayoptionally include: wherein acknowledgements are received from the UEfor PDSCH transmissions in subframes of the bundling window in a PUCCHof a subsequent uplink subframe where the PUCCH contains uplink controlinformation (UCI) with a two-bit acknowledgement field.

In Example 14, the subject matter of Example 13 may optionally include:wherein the value of the two-bit acknowledgment field in the UCI iscombined with the PUCCH resource selected by the UE to transmit thePUCCH from among the PUCCH resource indices computed by the UE for PDSCHtransmissions in subframes of the bundling window to derive up to fourseparate acknowledgements.

In Example 15, a machine-readable medium contains instructions that,when executed, cause a machine to carry out the methods according to anyof Examples 1 through 14.

In Example 16, a system comprises means for carrying out the methodsaccording to any of Examples 1 through 14.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that may bepracticed. These embodiments are also referred to herein as “examples.”Such examples may include elements in addition to those shown ordescribed. However, also contemplated are examples that include theelements shown or described. Moreover, also contemplate are examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

Publications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference(s) are supplementaryto that of this document; for irreconcilable inconsistencies, the usagein this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term, “or” is used to refer to a nonexclusive or, suchthat “A or B” includes “A but not B,” “B but not A,” and “A and B,”unless otherwise indicated. In the appended claims, the terms“including” and “in which” are used as the plain-English equivalents ofthe respective terms “comprising” and “wherein.” Also, in the followingclaims, the terms “including” and “comprising” are open-ended, that is,a system, device, article, or process that includes elements in additionto those listed after such a term in a claim are still deemed to fallwithin the scope of that claim. Moreover, in the following claims, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to suggest a numerical order for their objects.

The embodiments as described above may be implemented in varioushardware configurations that may include a processor for executinginstructions that perform the techniques described. Such instructionsmay be contained in a machine-readable medium such as a suitable storagemedium or a memory or other processor-executable medium.

The embodiments as described herein may be implemented in a number ofenvironments such as part of a wireless local area network (WLAN), 3rdGeneration Partnership Project (3GPP) Universal Terrestrial Radio AccessNetwork (UTRAN), or Long-Term-Evolution (LTE) or a Long-Term-Evolution(LTE) communication system, although the scope of the invention is notlimited in this respect. An example LTE system includes a number ofmobile stations, defined by the LTE specification as User Equipment(UE), communicating with a base station, defined by the LTEspecifications as eNode-B.

Antennas referred to herein may comprise one or more directional oromnidirectional antennas, including, for example, dipole antennas,monopole antennas, patch antennas, loop antennas, microstrip antennas orother types of antennas suitable for transmission of EE signals. In someembodiments, instead of two or more antennas, a single antenna withmultiple apertures may be used. In these embodiments, each aperture maybe considered a separate antenna. In some multiple-input multiple-output(MIMO) embodiments, antennas may be effectively separated to takeadvantage of spatial diversity and the different channel characteristicsthat may result between each of antennas and the antennas of atransmitting station. In some MIMO embodiments, antennas may beseparated by up to 1/10 of a wavelength or more.

In some embodiments, a receiver as described herein may be configured toreceive signals in accordance with specific communication standards,such as the Institute of Electrical and Electronics Engineers (IEEE)standards including IEEE 802.11-2007 and/or 802.11(n) standards and/orproposed specifications for WLANs, although the scope of the inventionis not limited in this respect as they may also be suitable to transmitand/or receive communications in accordance with other techniques andstandards. In some embodiments, the receiver may be configured toreceive signals in accordance with the IEEE 802.16-2004, the IEEE802.16(e) and/or IEEE 802.16(m) standards for wireless metropolitan areanetworks (WMANs) including variations and evolutions thereof, althoughthe scope of the invention is not limited in this respect as they mayalso be suitable to transmit and/or receive communications in accordancewith other techniques and standards. In some embodiments, the receivermay be configured to receive signals in accordance with the UniversalTerrestrial Radio Access Network (UTRAN) LTE communication standards.For more information with respect to the IEEE 802.11 and IEEE 802.16standards, please refer to “IEEE Standards for InformationTechnology—Telecommunications and Information Exchange betweenSystems”—Local Area Networks—Specific Requirements—Part 11 “Wireless LANMedium Access Control (MAC) and Physical Layer (PHY), ISO/IEC8802-11:1999”, and Metropolitan Area Networks—Specific Requirements—Part16: “Air Interface for Fixed Broadband Wireless Access Systems,” May2005 and related amendments/versions. For more information with respectto UTRAN LTE standards, see the 3rd Generation Partnership Project(3GPP) standards for UTRAN-LTE, release 8, March 2008, includingvariations and evolutions thereof.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with others. Otherembodiments may be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure, forexample, to comply with 37 C.F.R. § 1.72(b) in the United States ofAmerica. It is submitted with the understanding that it will not be usedto interpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. However, the claims may not set forth everyfeature disclosed herein as embodiments may feature a subset of saidfeatures. Further, embodiments may include fewer features than thosedisclosed in a particular example. Thus, the following claims are herebyincorporated into the Detailed Description, with a claim standing on itsown as a separate embodiment. The scope of the embodiments disclosedherein is to be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled.

What is claimed is:
 1. A method comprising: receiving, at a userequipment (UE), downlink control information (DCI) on an enhancedphysical downlink control channel (EPDCCH) that includes indexedenhanced control channel elements (ECCEs), the DCI to schedule aphysical downlink shared channel (PDSCH) resource for a downlinksubframe; receiving an acknowledgment resource offset (ARO) value in anARO field of the DCI that instructs the UE to shift the PUCCH resourceindex by an amount equal to the value of the ARO; and determining aphysical uplink control channel (PUCCH) resource index to acknowledgePDSCH transmissions as a function of the lowest ECCE index used toconstruct the EPDCCH, wherein the value of the ARO field corresponds toan ARO value to shift the PUCCH resource index to a range used foracknowledging PDSCH transmissions in the earliest subframe of a bundlingwindow, wherein, for a downlink subframe having a relative index mbetween 0 and M−1 with M being the number of subframes in the bundlingwindow and with m=0 representing the earliest subframe, the PUCCHresource index n_(PUCCH) ⁽¹⁾ is used to determine the resource blockpair, cyclic shift, and orthogonal cover sequence of a format 1 PUCCHand is computed as:$n_{PUCCH}^{(1)} = {n_{{ECCE},q} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + \Delta_{ARO} + N_{{PUCCH}.q}^{({e\; 1})}}$for an EPDCCH set q configured for distributed transmission to the UEand$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCHtransmitted in subframe m, N_(PUCCH,q) ^((e1)) is an offset configuredby the eNB to separate PUCCH resource indices computed for EPDCCH set qfrom those computed for other EPDCCH sets, Δ_(ARO) is the value of theARO contained in the DCI, N^(ECCE,q,i) is the number of ECCEs in EPDCCHset q configured for the UE in a subframe with relative index i, N_(RB)^(ECCE,q) is the number of ECCEs in a resource block, and n′ isdetermined from the antenna port used for EPDCCH transmission insubframe m.
 2. The method of claim 1, wherein, for m>0, the value of theARO field corresponds to an ARO value selected from the following set ofelements:$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 1},0,2} \right\}.$3. The method of claim 1, wherein, for m=0, the value of the ARO fieldcorresponds to an ARO value selected from the following set of elements:{−2, −1, 0, 2}.
 4. The method of claim 1, wherein the PUCCH resourceindex is calculated further based on EPDCCH added to the number of ECCEsin EPDCCHs derived for the UE and added to an integer value determinedfrom the antenna port used for EPDCCH transmission.
 5. A methodcomprising: transmitting, by an evolved NodeB (Enb) downlink controlinformation (DCI) on an enhanced physical downlink control channel(EPDCCH) that includes indexed enhanced control channel elements(ECCEs), the DCI to schedule a physical downlink shared channel (PDSCH)resource for a downlink subframe; assigning a physical uplink controlchannel (PUCCH) resource index to a user equipment (UE) foracknowledging the PDSCH transmissions as a function of the lowest ECCEindex used to construct the EPDCCH; and transmitting an acknowledgmentresource offset (ARO) in an ARO field of the DCI that instructs the UEto shift the PUCCH resource index by an amount equal to the value of theARO, wherein the value of the ARO field corresponds to an ARO value toshift the PUCCH resource index to a range used for acknowledging PDSCHtransmissions in the earliest subframe of a bundling window, wherein,for a downlink subframe having a relative index m between 0 and M−1 withM being the number of subframes in the bundling window and with m=0representing the earliest subframe, the PUCCH resource index n_(PUCCH)⁽¹⁾ is used to determine the resource block pair, cyclic shift, andorthogonal cover sequence of a format 1 PUCCH and is computed as:$n_{PUCCH}^{(1)} = {n_{{ECCE},q} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + \Delta_{ARO} + N_{{PUCCH}.q}^{({e\; 1})}}$for an EPDCCH set q configured for distributed transmission to the UEand$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCHtransmitted in subframe m, N_(PUCCH,q) ^((e1)) is an offset configuredby the eNB to separate PUCCH resource indices computed for EPDCCH set qfrom those computed for other EPDCCH sets, Δ_(ARO) is the value of theARO contained in the DCI, N_(ECCE,q,i) is the number of ECCEs in EPDCCHset q configured for the UE in a subframe with relative index i, N_(RB)^(ECCE,q) is the number of ECCEs in a resource block, and n′ isdetermined from the antenna port used for EPDCCH transmission insubframe m.
 6. The method of claim 5 wherein, for m>0, the value of theARO field corresponds to an ARO value selected from the following set ofelements:$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 1},0,2} \right\}.$7. The method of claim 5, wherein, for m=0, the value of the ARO fieldcorresponds to an ARO value selected from the following set of elements:{−2, −1, 0, 2}.
 8. The method of claim 5, wherein the PUCCH resourceindex is calculated further based on EPDCCH added to the number of ECCEsin EPDCCHs derived for the UE and added to an integer value determinedfrom the antenna port used for EPDCCH transmission.
 9. A non-transitorycomputer-readable medium including instructions that, when executed onprocessing circuitry of an evolved NodeB (eNB), cause the eNB to:transmit downlink control information (DCI) on an enhanced physicaldownlink control channel (EPDCCH) that includes indexed enhanced controlchannel elements (ECCEs), the DCI to schedule a physical downlink sharedchannel (PDSCH) resource for a downlink subframe; assign a physicaluplink control channel (PUCCH) resource index to a user equipment (UE)for acknowledging the PDSCH transmissions as a function of the lowestECCE index used to construct the EPDCCH; and transmit an acknowledgmentresource offset (ARO) in an ARO field of the DCI that instructs the UEto shift the PUCCH resource index by an amount equal to the value of theARO, wherein the value of the ARO field corresponds to an ARO value toshift the PUCCH resource index to a range used for acknowledging PDSCHtransmissions in the earliest subframe of a bundling window, wherein,for a downlink subframe having a relative index m between 0 and M−1 withM being the number of subframes in the bundling window and with m=0representing the earliest subframe, the PUCCH resource index n_(PUCCH)⁽¹⁾ is used to determine the resource block pair, cyclic shift, andorthogonal cover sequence of a format 1 PUCCH and is computed as:$n_{PUCCH}^{(1)} = {n_{{ECCE},q} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + \Delta_{ARO} + N_{{PUCCH}.q}^{({e\; 1})}}$for an EPDCCH set q configured for distributed transmission to the UEand$n_{PUCCH}^{(1)} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{({e\; 1})}}$for an EPDCCH set q configured for localized transmission to the UEwhere n_(ECCE,q) is the lowest ECCE index used to construct the EPDCCHtransmitted in subframe m, N_(PUCCH,q) ^((e1)) is an offset configuredby the eNB to separate PUCCH resource indices computed for EPDCCH set qfrom those computed for other EPDCCH sets, Δ_(ARO) is the value of theARO contained in the DCI, N_(ECCE,q,i) is the number of ECCEs in EPDCCHset q configured for the UE in a subframe with relative index i, N_(RB)^(ECCE,q) is the number of ECCEs in a resource block, and n′ isdetermined from the antenna port used for EPDCCH transmission insubframe m.
 10. The non-transitory computer-readable medium of claim 9wherein, for m>0, the value of the ARO field corresponds to an ARO valueselected from the following set of elements:$\left\{ {{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 2},{{- {\sum\limits_{i = 0}^{m - 1}N_{{ECCE},q,i}}} - 1},0,2} \right\}.$11. The non-transitory computer-readable medium of claim 9 wherein, form=0, the value of the ARO field corresponds to an ARO value selectedfrom the following set of elements: {−2, −1, 0, 2}.
 12. Thenon-transitory computer-readable medium of claim 9, wherein the PUCCHresource index is calculated further based on EPDCCH added to the numberof ECCEs in EPDCCHs derived for the UE and added to an integer valuedetermined from the antenna port used for EPDCCH transmission.